Web Vocabulary Profiler - Enter a text and the program will tell you: how many word types the text contains from the following four frequency levels: (1) the list of the most frequent 1000 word families; (2) the list of the second 1000 word families; (3) the Academic Word List; (4) the words that do not appear in any of the preceding lists.

English language learning sites

BBC World Service - Learning materials based on news and current affairs. Also discussion forums.

Professional Word Web - "The Professional Word Web aims to help students learn the words they need for their academic studies and future careers." By the University of Hong Kong, Vocabulary for Business, Law, Social Work and Engineering.